1. Field of the Invention
This invention relates to a radiation image read-out apparatus for use in a radiation image recording and reproducing system. This invention particularly relates to a radiation image read-out apparatus suitable for image read-out from a stimulable phosphor sheet for dental image recording and for other purposes. This invention also relates to a stimulable phosphor sheet composite member comprising a stimulable phosphor sheet and a means for shielding the stimulable phosphor sheet from light, particularly a stimulable phosphor sheet composite member suitable for dental image recording and for other purposes.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. Nos. 4,258,264, 4,276,473, 4,315,318 and 4,387,428 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet) is first exposed to a radiation passing through an object such as the human body to have a radiation image of the object stored thereon, and is then scanned with stimulating rays such as a laser beam which cause it to emit light in proportion to the stored radiation energy. The light emitted by the stimulable phosphor sheet upon stimulation thereof is photoelectrically detected and converted to electric image signals, and the radiation image of the object is reproduced as a visible image by use of the image signals on a recording material such as a photographic film, a display device such as a cathode ray tube (CRT), or the like.
It has heretofore been known that the aforesaid radiation image recording and reproducing system using the stimulable phosphor sheet is utilized for diagnosis or viewing of a comparatively large object portion such as the head, the chest or the limb. It is also considered that the radiation image recording and reproducing system be utilized for dental image recording by use of a small stimulable phosphor sheet.
With the conventional radiation image recording and reproducing system, the stimulable phosphor sheet is generally subjected to image recording in the form housed in a cassette for housing a single stimulable phosphor sheet, and is then taken out of the cassette and processed for image read-out in a read-out apparatus. However, in the case of the dental image recording, it is not always possible to carry out the image recording by using of the aforesaid cassette, and it is necessary for the surface of the stimulable phosphor sheet to be provided with a light shielding means of a smaller scale than the cassette. Also, the stimulable phosphor sheet for use in the dental image recording must be markedly smaller than the stimulable phosphor sheet used in the aforesaid conventional image recording. Thus the stimulable phosphor sheet for the dental image recording is different in the light shielding means, the size and other factors from the conventional stimulable phosphor sheet, and therefore it is not always possible to carry out the image read-out from the stimulable phosphor sheet for the dental image recording by use of the conventional read-out apparatus.